Royal Enfield CONSTELLATION 1958, Workshop Maintenance Manual

Page: 57 / 106

With more cut-away on the air intake side (or
vice versa if weak).
(iv) Jet Needle Position. Tuning sequence
(ii) and (iii) will affect carburation up to some-
where over one-quarter throttle, after which the
needle (which is suspended from the throttle
valve comes into action and when the throttle is
opened, further and tests are again made for rich
or weak spots (as previously outlined) the
needle can be raised to enrich or lowered to
weaken the mixture whichever may be found
necessary. With these adjustments correctly
made, and the main jet size settled, a perfectly
progressive mixture will be obtainable from
tick-over to full throttle.
mixture, and anti-clockwise to enrich it. Adjust
this very gradually until a satisfactory tick-over
is obtained, but take care that the achievement of
too slow a tick-over - that is, slower than is
actually necessary-does not lead to a "spot"
which may cause stalling when the throttle is
very slightly open.
(iii) Throttle Cut-away. Having set the pilot
adjuster, open up the throttle progressively and
note positions where, if at all, the exhaust note
becomes irregular. If this is noticed, leave the
throttle open at this position and close the air
lever slightly; this will indicate whether the spot
is rich or weak. If it is a rich spot, fit a throttle
valve
Section F3 Page 4
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